1. Field of the Invention
The present invention relates to an image processing apparatus and, more particularly, to retrieval of moving image data.
2. Related Background Art
With the recent advances in high-speed computers and large-capacity memories, a great deal of attention has been paid to techniques of processing digital moving images with computers as multimedia techniques.
Compression techniques are indispensable for processing moving images because of their enormous data amounts.
As a moving image compression scheme which has recently been standardized, MPEG 1 (Moving Picture Image Coding Expert Group Phase 1) is available.
The principle of a high-efficiency coding scheme based on MPEG will be described below.
In this high-efficiency coding scheme, redundancy in the time-axis direction is reduced by calculating differences between frames, and the resultant difference data is subjected to DCT (Discrete Cosine Transform) and variable-length coding processing to reduce redundancy in the spatial direction, thereby realizing high-efficiency coding as a whole.
With regard to redundancy in the time-axis direction, since there is a high correlation between consecutive frames of moving images, the redundancy can be reduced by calculating differences between a frame to be encoded and a preceding or succeeding frame.
In addition, according to MPEG, the redundancy is further reduced by motion compensation.
More specifically, differences between a macro-block corresponding to a target frame and each of macro-blocks near a block corresponding to a preceding or succeeding frame are calculated in units of a predetermined number of blocks (in units of macro-blocks), providing that each block consists of (8xc3x978) pixels and each macro-block consists of four blocks of luminance data and two blocks of color difference data. A macro-block exhibiting the minimum differences is then searched out to detect a motion vector. This motion vector is encoded as data.
In a decoding operation, the macro-block data corresponding to the preceding or succeeding frame is extracted by using this motion vector, thereby decoding the data encoded by using motion compensation. The size of an image to be encoded is based on an SIF format, i.e., 360 pixelsxc3x97240 lines for a luminance signal, and 180 pixelsxc3x97120 lines for a chrominance signal.
MPEG 1 is used to display reproduced images while decoding moving image data compressed/stored as codes in a CD-ROM or the like in real time.
Owing to high compression efficiency, applications of MPEG 1 to a coding scheme for storing various moving image data in the hard disk of a computer, a magneto-optical disk, and the like have been proposed.
In general, a name is assigned to each sequence of stored moving images to manage each moving image.
A search for a sequence corresponding to a given name is made as needed, and the corresponding codes are reproduced/displayed on a computer display.
The following problems are posed in the above prior art in managing moving images by assigning a name to each sequence:
(1) Since the number of characters of a name is limited because of the limitation of a database or the like, it is difficult for a user to assign a name which allows easy retrieval.
(2) It is difficult for the user to retrieve a sequence by a name assigned by another person, retrieval must be performed by reproducing sequences at random.
The present invention has been made in consideration of the above situation, and has as its object to provide an image processing apparatus which improves the retrieval efficiency of moving image data and the operability in retrieving the data.
In order to achieve the above object, according to an aspect of the present invention, there is provided an image processing apparatus comprising moving image input means for inputting a plurality of moving image data, forming means for forming still image data associated with the moving image data, and retrieval means for retrieving desired moving image data on the basis of the still image data formed by the forming means.
According to another aspect of the present invention, there is provided an image processing apparatus comprising moving image input means for inputting moving image data, still image input means for inputting a still image, storage means for storing the moving image upon associating the image with the still image, and reproduction means for reproducing the moving image on the basis of the still image.
Other objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.